Re: thin slides=longer staining

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From:Geoff McAuliffe <mcauliff@UMDNJ.EDU>
Content-Type:text/plain; charset=us-ascii wrote:

> I was a little surprised that more people didn't pick up on this--thinner
> slides (ex: 3 microns) need to be stained longer....there just isn't the
> amount of cellular material there to absorb stain....also, years ago when the
> special stains were developed the ability to cut sections at 3 microns had
> not been achieved..therefore, the times used in the stains were all developed
> for those 5 micron sections....

    This was what I was taught and it has been my experience as well. I have
"done the experiment" with 0.25, 0.5, 1.0 and 2.0 micron plastic sections
(Araldite, Epon). I have also found that novice TEM students want to cut sections
as thin as possible, then have great difficulty getting enough contrast under the
beam. In both instances thicker sections = more tissue = better contrast, even
without any staining (other than osmium).
    In paraffin-embedded tissue, I suspect that what membranes remain are not
much of a barrier to diffusion, unless times are very short or the stain
molecules are very large.

Geoff McAuliffe, Ph.D.
Neuroscience and Cell Biology
Robert Wood Johnson Medical School
675 Hoes Lane, Piscataway, NJ 08854
voice: (732)-235-4583; fax: -4029

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